1. Field of the Invention
The present invention concerns a sheathing for veins, a method for its manufacture, and its application in surgery.
2. Description of the Related Art
Medicine is frequently confronted with the task of treating cardiovascular diseases, such as arteriosclerosis for instance, caused by changes in blood vessels. Modern surgery employs, in addition to, e.g., deobliteration methods, substitute-vessel implants in the form of bypasses for reconstructing arterial vessels. Known, for example, are vessel implants manufactured from synthetic materials, or synthetic materials combined with natural materials.
Detrimental interactions with the physiological environment in patients' bodies may occur if full-synthetic materials are employed. Serious complications, such as thrombosis or restenosis of vessel implants, that may require expensive post operations may occur when synthetic materials are substituted for coronary or peripheral vessels with small lumen. It is thus desirable to employ implants formed from natural vessel material, since they beneficially affect natural endothelialization and the anti thrombogenic properties of vessel walls. Such biological substitute-vessel materials are generally obtained from veins. However, implanting veins in the arterial vessel system may cause increases in wall thickness to occur during arterialization. If those increases are accompanied by intimahyperplasy due to the differing compliances of veins and arteries, they may ultimately lead to restenosis of the implants. It will be beneficial to externally encase or reinforce native veins in order that they will be reliably able to perform their intended function as, for example, a coronary or peripheral bypass for arterial blood transport, over the long term. External sheathing or stiffening ribs can adapt the compliance of natural vein material to suit the arterial system and thus both reduce incidences of intimahyperplasy and allow achieving high non closure rates over the long term. Moreover, the aforementioned sheathing will also allow implantation of varicose, ectatic, or thin-walled veins that have not been employed to date due to their unfavorable hemodynamic properties. The latter will be the only means for employing vessel materials from patients' own bodies as substitutes for vessels having small lumen, particularly in the case of patients suffering from multiple vessel imperfections.
A vessel prosthesis where a woven sheathing is drawn over a natural blood vessel is known from German Patent DE 4340755. A natural blood vessel spirally wrapped in crossed fibers is described in European Patent EP 687164. U.S. Pat. No. 5,645,581 discloses a tube, whose manufacture is described in U.S. Pat. No. 5,755,659, having crossed fibers spirally wrapped around its longitudinal axis.
According to German Patent DE 19910340, a tube, sheath, or tubing is employed as sheathing for a vein to be used as artery prosthesis. An external reinforcement for vessel prostheses having a duo layer, tubular, polymer-fiber sheathing is known from World Patent WO 00/54703.
The known reinforcements for vessel material have a number of disadvantages. For example, numerous, complex, procedures are required for preparing them and attaching them to implant vessels. Additional tissue adhesives are required in order to attach the reinforcements. Reinforcements based on metals may adversely impact handling of prostheses and foster incompatibility reactions. Problems, particularly problems in the anastomosis area, may occur due to loose ends of wires.
The problem addressed by the invention is thus making available a sheathing for veins that will overcome the problems arising from the state of the art, will reinforce veins to be employed as surgical implants for use as durable vessel substitutes, may be simply and inexpensively manufactured following ordinary manufacturing procedures and manufactured on ordinary manufacturing equipment, and will be simply and reliably applicable in surgery.